Owners of certain kinds of plastic pipes on propane or natural gas-fired boilers, take note: The terms of a 10-year-old recall are about to change.

The 1998 recall affected about 250,000 high-temperature plastic vent, or HTPV, pipes manufactured under the names Plexvent, Plexvent II or Ultravent. The pipes were recalled to avoid the possibility that they might crack or loosen at the joints, causing deadly carbon monoxide to escape into consumers’ homes.

In its original recall notice, the Consumer Product Safety Commission noted that only gray or black plastic pipes were involved in the recall. In furnaces, only pipes that went through the sidewall of a structure (horizontal systems) were subject to the recall; in boilers, all HTPV pipes were involved. No other plastic pipes, such as white PVC, were involved.

About two dozen manufacturers of HTPV pipes took part in the recall effort after the first case in which the safety commission used mediation to bring all segments of an industry together to benefit consumers. Those who bought the recalled pipe systems were eligible for professionally installed replacements at no cost.

The safety commission has issued a new alert, announcing a change effective May 1. After that date, owners of the recalled systems will be eligible for rebates of up to $400 for Plexvent systems and up to $250 for Ultravent. Those rebates would go toward either an HTPV replacement system or a new, high-efficiency system from the same manufacturer that does not require HTPV.

Clearly, it’s in the interest of owners of older HTPV systems to act before May 1 to qualify for both replacement and free installation of a safer system. Owners of such systems can check their pipes, looking for the names Plexvent, Plexvent II or Ultravent either printed on the pipes or on labels attached to them. The pipes will be either gray or black, and they will be in boiler systems or, in the case of a furnace, go through a structural sidewall.

Owners are urged to call 800-758-3688 between 8 a.m. and 7 p.m. Monday through Friday to sign up for HTPV replacement.

Check the safety commission’s Web site at www.cpsc.gov for a list of manufacturers taking part in the recall program. You can also sign up to receive such alerts from the agency, involving recalls or other subjects of interest to consumers.

A note about last week’s column on advance check scams. At mid-morning Monday, a woman in the Bangor area called Maine’s Bureau of Financial Institutions to report that she had been considering accepting an offer such as the ones described in the column. When she read it, she quickly changed her mind. We applaud all consumers who read, learn and share their knowledge with others.

Consumer Forum is a collaboration of the Bangor Daily News and Northeast CONTACT, Maine’s membership-funded, nonprofit consumer organization. Individual and business memberships are available at modest rates. For assistance with consumer-related issues, including consumer fraud and identity theft, or for more information, write: Consumer Forum, P.O. Box 486, Brewer 04412, or e-mail contacexdir@live.com.